Our average high on the first of September is eighty four with an average low downtown of sixty seven. By the end of the month our average high falls to a near perfect seventy five with an average low of fifty seven. It will warm up a bit today and over the weekend.
The hottest temperature recorded in September is 104 set on the seventh back in 1881. The lowest reading recorded was 36 on the twenty third of the month in 1879. National Airport averages just over 3.75 inches of rain while Dulles average rainfall is 3.83" for the month. (At this writing we are already over 4" at both National and Dulles.) The wettest September on record occurred back in 1935 when we received almost 17.5 inches of rain. The driest September was back in 2005 when we recorded a meager 0.11 of an inch of rain. It's hard to believe that none of Katrina's remnants ever made it to the Metro Area, or anywhere in the Mid Atlantic for that matter.
If you suffer from allergies, weeds and grasses will be your main enemies in September with weeds leading the way by the end of the month. Frost will mark the end of the pollen season and that is still probably six weeks or more away.
Although astronomical fall doesn't begin until the fall equinox September 22nd, "meteorological fall" begins on September 1st. September, October and November comprise meteorological fall. For the sake of weather records, the four seasons are broken into three even months. This September we will see a new moon on September 5th and a full Harvest moon on Thursday the 19th. On the 8th, shortly after sunset, the crescent moon will be below Venus with a bright white star, Spica to the lower right. On the 19th Venus and Saturn will pass "close" to each other but the full moon will competing for your gaze as well.